Boeing B-17 Flying Fortress

The Boeing B-17 Flying Fortress was the first mass-produced, four-engine heavy bomber. The B-17 was designed in 1934 and the first prototype flew on 28 July 1935. Only a few were produced before the U.S. entered World War II in December 1941, but production quickly ramped up thereafter. The first use of the B-17 was against Wilhelmshaven on 8 July 1941. The B-17 not only pounded enemy strategic targets, but also carried out the destruction of enemy fighter aircraft. Massed formations of B-17s downed hundreds of the fighters sent to oppose them, causing the loss of enemy planes and irreplaceable pilots.

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Photo Gallery:  (approximately 80 original photos) Boeing aircraft plant, Seattle, Washington. Also factory employees at Boeing aircraft plant assembling the B-17 etc.

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Vulnerable Flying Fortress

To call so legendary a giant as the Flying Fortress 'vulnerable' may sound ridiculous. However, this mighty bomber, the backbone of the US 8th Army Air Force effort against Germany, was in its early days in the European theatre dismal proof that the bomber would not 'always get through'. On the contrary, the fighter was more likely to get through to the insufficiently protected bomber. This truth did not fully dawn on the Americans until 1943, when a period of relative immunity ended and battles between the nimble German fighters and heavily-loaded B17F Flying Fortresses, which flew at only 180 mph (290 kph), saw the latter losing primacy. In September/October, B17 losses reached a prohibitive ten per cent per raid, and the need to increase protection became paramount. Apart from providing fighter escorts, which were not always able to make the there-and-back trip, the logical thing to do was to increase the bombers' own armament. Not until this was done did the Flying Fortress begin to earn its legendary reputation as the mightiest weapon the 8th Army Air Force possessed in its bombing offensive against Germany.

In its original prototype form, the B17's armament was almost pitiful. It consisted of only five machine guns - one .3 in (7.62 mm) in the nose and two .5 in (12.7 mm) on each fuselage side. It was a very different matter of self-defense when production B17s acquired another eight .5 in (12.7 mm) guns in dorsal, ventral, waist and tail positions, and in the B17G of late 1943, thirteen .5 in (12.7 mm) Browning machine guns in the new chin turret, the cheek ventral, dorsal, waist and tail positions. In addition, fourteen B17Fs were converted into huge flying gun-platforms, the YB40s, with extra power turret amidships, twin .5 in (12.7 mm) waist guns and remote-controlled twin-gun turret under the nose. In all, the YB40, which flew at the vulnerable edges of the Flying Fortress 'boxes' had sixteen .5 in (12.7 mm) guns, including two in the nose side-windows. It was also a flying arsenal: although it carried no bombs, its store of machine-gun ammunition was practically inexhaustible.

The Boeing B-17 Flying Fortress earned a reputation for toughness and versatility as the design of the B-17 went through eight major changes during its production history. The final version was the B-17G, designed to eliminate a weakness in head-on attacks by adding a chin turret with two .50 cal. machine guns under its nose. The B-17G was both new production and conversion of existing planes, for a total of 8,680 built.

Boeing B-17

The 'Flying Fortress'

The Boeing B-17 began life as the Boeing 299 which first flew in July 1935. This latter aircraft, built in answer to a specification of the previous year, was a four-engine bomber of clean lines powered by 750 hp Pratt & Whitney Hornet engines. It had a nine-man crew and carried a 2,724-kg (6,000-lb) bomb load. The United States Army Air Corps tested 13 YB-17As in early 1937 and the last was modified for high altitude bombing with Wright Cyclone engines with turbo-superchargers fitted.

The first production model was the B-17B and by March 1940 39 had been delivered. The RAF received 20 B-17Cs for combat evaluation and subsequent American design incorporated their experience in the B-17D and E models. The B-17E (RAF Fortress II) entered production in 1942 and was fitted with armor, three new turrets - tail, ball and front upper - housing .50-inch machine-guns. Tailplane improvements gave greater stability as a bombing platform, and with the Norden bomb-sight the Fortress was to become a devastating weapon. Boeing, Vega and Douglas produced 512 of these examples and it formed the mainstay of the US Eighth Army Air Force flying high altitude strategic bombing missions from UK bases during and after 1942. The B17F had paddle-bladed propellers and a different nose; over 3,400 were built.

But the major production version was the B17G. To counter Luftwaffe attacks a chin turret and waist gun positions were fitted, increasing the crew to ten, and it was in the B-17G that the USAAF really carried the war to Germany. 8,680 were built, of which the RAF received some, and the thunder of their 1,200 hp Wright R-1820-97 supercharged Cyclone engines was heard almost daily over East Anglia until the war's end. Other uses to which the B-17 was put included recce, gunship and air-sea rescue tasks, and some were converted into BQ7 'Aphrodite' radio-controlled flying bombs with 5,340 kg (12,000 lb) of high explosive.